Lubricated refrigerant compressor



March 3, 1942. J. ,TOUBORG 4 2,274,942

LUBRICATED REFRIGERANT COMPRESSOR Filed March 30, 1940 INVENTOR J-ns 7bubg1y atented Mar. 3, 1942 UNITED STATES, PATENT OFFICE LUBRICATED BEFRIGERANT COMPRESSOR Jens Touborg, Tecumseh, Mich, Application March 30, 1940, Serial No.'327,063

2 Claims.

This invention relates to compressors, and it has particular reference to the provision of improved means for automatically supplying limited quantities of .lubricant to the head end of the piston and cylinder assembly, during operation of the apparatus.

While the present invention is generally applicable to compressors, it will herein be described with particular reference to a hermetic compressor employed in an artificial refrigeration system. In the well-known compressor-condenser-expander type of refrigerating machine, the refrigerant vapor is compressed, delivered to the condenser where the hot vapors are cooled, and then to the expansion coil wherein the refrigerant volatilizes with absorption of heat. The expanded vapors are then returned to the compressor for compression, to repeat the cycle. More or less oil is picked up by the refrigerant during its passage through the compressor, and is carried into the remaining parts of the system where it tends to remain, thus decreasing the eiliciency of operation. Accordingly, one objective in designing refrigeration compressors and systems has been to provide means for minimizing this oil circulation, and, generally speaking, it may be said that, at this date, the problem of keeping an excess of oil out of the condenser and expander has been reasonably well solved.

Insofar as the necessary function of supplying lubricant to the moving parts of the compressor itself is concerned, it may also be noted that the art has been inclined to deem this problem no longer of serious consequence. Thus, by immersing the parts, or some of them, in an oil bath, by providing oil. ducts and the like between suitable points, the art has assumed that a sumcient supply of oil is made available.

However, as I now find, these diametrically opposed desiderataF-namely, keeping theoil out of the compressed refrigerant, but getting adequate oil to'all working parts-have not been both entirely satisfied, and the primary purpose of this invention is to provide means whereby both purposes are effectively achieved.

By way of preliminary explanation of the underlying principle of this invention, as I now understand the same, it may be noted that a compressor, operating in an entirely satisfactory manner under normal loads, will suddenly develop a knock or noise in the presence of high or abnormal head pressures. Examination of returning refrigerant, as by passing it through a sight-glass, will show a reasonable freedom from excess amounts of oil, while examination of the lubricating ducts and the like will show that they are free and open, so that plenty of oil ought to flow to all the working parts. The noise, however wlll continue as long as the head pressures remain high, and as such noises are frequently indicative of faulty lubrication, the question presented is as to the cause of the noise.

I find that such noises 01' knocks result from the pressure effect of the refrigerant on the oil film between the piston and cylinder wall, wherein the oil is actually blown back into its several passages by the pressure of the abnormally compressed refrigerant, with the result that the head end, and the valves, are operating in a substantially dry, or unlubricated condition. Upon attempting to correct this difficulty by making the oil passages larger, on of two undesirable results obtain. First, there may be so much oil admitted as to saturate the discharged refrigerant during normal operation, which, as noted above, is not desirable. Second, the head pressure, if suficiently high, continues to block lubrication of the terminal portions of the piston, and thus nothing is accomplished.

In order to eliminate this defect of dry head ends, and at the same time prevent the admixture of undue amounts of oil with the compressed refrigerant, I now propose to design the head end of the compressor in such manner that the vapor pressure itself becomes the means of automat ically forcing adequate quantities of lubricant into the head end of the cylinder whenever head pressures rise above a predetermined normal.

The invention will be more clearly understood from the following detailed description of a specific embodiment thereof, illustrated in the accompanying drawing, wherein:

Fig. l is a section of a hermetic compressor of a type utilized in refrigeration service; and,

Fig. 2 is an enlarged fragmentary section of the head end of the compressor, showing the novel oil passages in greater detail.

For illustrative purposes, the invention is shown organized with a refrigerant compressor unit of the hermetic type, wherein an integrated twopart casing is, ii encloses acompressor mechanism l2 and the motor It for driving the same. The frame for the compressor mechanism l2 consists of a single casting i5 having a crankcase portion it, a cylinder block portion H, and an enlarged upstanding circular flange 18. The casting is assembled with the casing by pressing the flange 18 into the upper part In of the casing. The stator IQ of the motor 13 is pressed into the interior of the flange l 8.

, posit it later on the cylinder wall.

The crankcase portion i6 is formed with a vertical bearing ii for rotatably receiving a crankshaft 20 which projects therethrough and is affixed to the overlying rotor 83a of the motor 113. The lower end of the crankshaft Ed is carried in a bearing block 23, which block is secured to an annular shoulder is on the portion it.

The cylinder block portion ll is bored to form a horizontal cylinder 25, and the cylinder is capped by-a head 26 and an interposed valve plate 26. A piston llil is mounted in the cylinder 25, and it carries a wrist pin 3i to which is fitted the small end bearing 32 of a connecting rod 33.

The other end of the rod 33 is formed-with a bearing strap portion d l'which is disposed about an eccentric portion Eta of the crankshaft it.

Lubricating oil is preferably conveyed to the various bearing surfaces under pressure by any suitable pumping means known in the art. In the present instance, a centrifugal pump is formed within the crankshaft it by drilling an off-center longitudinal passage'ilh and communicating radial passages 336, Bi, and 33 therein. i'he bottom of the crankshaft is formed with an aitialpassage ll which communicates with the passage 5 3t, and thus provides the eye portion of acentrifugal pump. An underlying thrust plate it. secured to the block 233, is drilled to permit the passage ll to receive oil from the surrounding oil body. Thus, the oil is forced up the passage 35 30 and out of the axial passages to lubricate the crankshaft bearing ti and bearing block 23, and also the eccentric strap El i. The connecting rod 333 is drilled through the strap 3%, as indicated by the numeral l l. so that oil is also supplied to the wrist pin 3i. The wrist pin iii (Fig. 2) contains an axial passage 55, through which oil is deposited on the wall of the cylinder The piston til is formed with oil grooves il, it and lit, and a terminal. pick-up groove the lattergroove clearing the cylinder at the hot= tom of the piston stroke, so that it may receive splashed lubricant from the crankcase and de- It will thus be seen that as the piston is reciprocated, the oil supplied by the groove lit and through the wrist pin ill, is spread over the surface of the cylinder wall to be later picked up by the oil groove, so that all but the end of the cylinder is amply provided with lubricant. The cylinder wall is formed with a partial groove or pocket M, which serves as a reservoir for the piston grooves.

Thus, as the piston reciprocates, a certain amount of oil picked up in the terminal groove 58 is wiped over the surface of the cylinder bore, while another amount of oil flows through the wrist pin passage 55, and is partially admitted to the groove 19. As the piston advances toward the head end, the passage tsisznpmentarily aligned with the reservoir 5!, and oil is then discharged directly therefrom into the reservoir to keep it filled. Oil in the duct i5 is, oi course, under pressure developed in the lubricating pump 36. As the grooves il and it pass the reservoir, for example, on the next stroke, they are replenished therefrom with oil, which is thus made available for lubricating the portions of the cylinder wall which they traverse, and for supplying oil to the hereinafter described port 65, to the extent that the head pressure indicates.

Refrigerant from the evaporative portions of the refrigeration system (not shown) is directed into the casing portion l0 through a fitting 52, and thence it is drawn into a suction pipe 53 leading downward to the cylinder block portion ll of the frame casting it. The block portion ll is formed with an inlet passage 55 communicating with the pipe 53, and also with a hole 55 in the valve plate 28, which hole leads to an inlet chamber 56 in the head 25. In efiect, the inlet passag 5t and hole 55 may be considered part of the inlet chamber 56. The inlet chamber 58 communicates with the cylinder bore through a port 56a in the plate 28, which port is closed by a leaf spring valve 511. The plate is also formed with an outlet port 5%, which is closed by a springpressed valve Gil. Thus, on the suction stroke of the piston, gaseous refrigerant is drawn into the cylinder bore 25 through the port 56a and, on the return stroke, the refrigerant is expelled under compression through the port 58 into an outlet chamber 65, whence it is directed out of the unit through a drilled passage 62 and a communi eating pipe d3.

It will be observed that the inlet passage 5t and the cylinder bore 25 are connected by a small vent port 65, which port is so disposed as to be always covered by the piston till. During operation of the compressor under normal loads, it will be apparent that the close running fit of the pistonin the cylinder, plus the oil film therebetween, will be sufiicient to prevent gas leakage or blow-by, and accordingly the port. 65 will remain functionally inoperative. When severe head pressures are encountered, however, the gas on the compression stroke of the piston will tend to displace the oil film between the piston and cylinder wall. In a well fitted piston, such penetration would probably not extend farther than the second oil groove as. This breakdown of the oil film causes what is known as dry knock and it is signal, in prior structures, that the upper portions of the cylinder wall are being, temporarily deprived of proper lubrication.

in the present invention the provision of the oil duct t5 provides an escape tor the oil directly into the inlet passage 53 whenever head pressures are suihciently .high as to cause gas penetration of the piston areas, as above outlined. In this event, it will be obvious that the gas pressure will force the oil contained in the grooves 5? and tie out of the port 35 and into the inlet passage $56. This occurs during the compression stroke of the piston when such grooves pass the port (i5. 0n the subsequent suction stroke of the piston, it will be seen that the small quantity of oil thus deposited in the inlet passage $41 will be drawn into the cylinder with the incoming charge, thus being deposited on the walls of the cylinder and providing adequate lubrication ior this portion of the cylinder upon the next passage of the piston.

When normal conditions in the system are gradually restored;- and toss pressures become correspondingly lower, the quantity of oil which escapes through the port as will become smaller in volume, until the oil carried by the piston is sumcient for complete lubrication of the cylinder wall. Thus, the port arrangement provides for automatic metering of oil to the upper areas of the cylinder in response to pressure variations in the system.

It is not intended that the invention be limited to the type and style of compressor herein illustrated, since it will be obvious to those'skilled in the art that the principle set forth may be incorporated, with slight modifications, in all types of compressors.

I claim:

1. In a compressor having a reciprocable piston mounted in a cylinder bore having a head end, and inlet and outlet chambers communicating with the cylinder bore, oil supply means for the head end cylinder portionsresponsive to pressure conditions in the outlet chamber, comprising a port extending into the cylinder bore and connecting the bore with the inlet chamber, said po"t being so located as to be covered by the piston during all phases of reciprocation thereof, oil grooves in th piston registering with the port during movement of the piston, and means for supplying oil to the grooves, whereby oil supplied to said grooves is periodically transmitted to the port and thence to the head end of the cylinder bore n response to said pressure conditions.

2. In a compressor having a reciprocable piston mounted in a cylinder bore having a head end and inlet and outlet chambers communicating with the cylinder bore, said inlet chamber having an extended passage portion disposed adjacent to the cylinder bore, oil supply means for the head end cylinder'portions responsive to pressure conditions in the outlet chamber, comprising a port connecting the cylinder bore with said extended passage, said port being so located as to be covered by the piston during all phases of reciprocation thereof, oil grooves in the piston registerable with the port during movement of the. piston, and means for supplying oil to the grooves, whereby oil supplied to said grooves is periodically transmitted to the port and thence to the head end of the cylinder bore in response to said pressure conditions.

JENS TOUBORG. 

